Embodiments disclosed herein relate to coatings employed on elements of a printing apparatus. In particular, embodiments disclosed herein relate to oleophobic anti-wetting coatings employed on the front face of a printhead.
In typical solid ink printhead configurations, a nozzle plate is provided with an array of jets through which the ink exits a jet stack. In some printhead systems, the nozzle plate and jet stacks comprise stainless steel plates, although recently these parts have been replaced with flexible, polymer layers such as polyimides. In some instances, the polyimide film receives an anti-wetting coating, bonded to a stainless steel aperture plate, and subsequently a laser ablates the array of apertures into the polyimide film.
Drooling nozzles, wetting and adhesion of ink on the printhead front face lead to missing and misdirectional jetting along with poor image quality. Drooling nozzles weep ink when the internal pressure of the printhead exceeds a particular pressure. The higher the pressure the nozzles can maintain without weeping the better the performance. Wetting occurs when the front face of the printhead remains wet after printing. This ink that remains on the printhead can block the nozzles resulting in missing nozzles and misdirectional printing. FIG. 1 shows a photograph of such a contaminated printhead.
One approach to address these issues employs an active cleaning blade system. The system purges ink from the printhead and a wiper blade then wipes the ink off of the front face. Ink purges typically occur after the system detects missing jets and after a power-down when the ink has frozen or solidified, shrunk and drawn air into the system. The ink purge expels contamination, trapped air and clears the nozzles, and then the wipers clean off the front face.
In conjunction with wiper blade systems, various anti-wetting coatings have been used to improve performance. Current coatings, while having good thermal and ink stabilities, may suffer from lower mechanical robustness than may be desirable, especially with the demands placed on such coatings when used in conjunction with wiper blade systems. Other issues may arise due to coating stability under printhead manufacturing conditions.